When testing patients for allergy, an epicutaneous test plaster is commonly used, which has a number of test chambers which in connection with use of the test plaster can be loaded with various allergens. The test chambers contain a filter paper for application or absorption of the allergens and are arranged at a suitable distance from each other to make it possible to separately assess the effect of the various allergens.
A prior-art epicutaneous test plaster, which is widely used, is made up of a flexible carrier with an adhesive layer for removable adhesion of the epicutaneous test plaster to the skin of the tested patient. The carrier is essentially made of a medical tape with a hypoallergen adhesive layer. The test chambers of this prior-art test plaster are formed as shallow square plastic cups with an outwardly directed flange. The test chambers are then fixed, spaced from each other, to the carrier of the epicutaneous test plaster and are distributed over the surface of the carrier in a suitable pattern. In the test chambers, a filter paper can be inserted to serve as an absorbent for allergen substances which are later to be inserted into the test chambers. A cover layer is applied over the test chambers and kept in place on the carrier by means of the adhesive layer of the carrier.
In a prior-art embodiment, the cover layer has the form of a blister sheet which is made of a suitable plastic material and has low blister rises with the same distribution and location as the test chambers. The blister rises have a larger inner width than the test chambers and extend down round the test chambers when the cover layer is applied to the epicutaneous test plaster and is kept in place by means of the adhesive layer of the carrier. By the cover layer being kept in place on the carrier by means of the adhesive layer of the carrier, the medical staff can remove the cover layer, load the test plaster with adequate allergens and then either directly perform the test of the patient or reseal the test plaster until it is to be used on a later occasion.
This known test plaster with a blister cover layer has great advantages owing to its composition and resealability and also the rigidity which is imparted to the test plaster by the cover layer and which facilitates handling. However, manufacture of this test plaster is associated with certain difficulties, inter alia, since the cup-shaped test chambers must be made separately and subsequently, in connection with mounting on the carrier, be oriented in the correct way and then secured to the carrier, and since it is difficult to attach the requisite filter paper in the test chambers without the use of adhesive for this purpose. Therefore the filter paper is applied manually on the actual patient testing occasion when using the known test plaster.
NL-8701577-A discloses and describes an allergy testing device which comprises a carrier with an adhesive layer for holding a flexible strip, which is made of a cellular plastic material with closed cells and which has punched-out portions to form test chambers. A moisture-proof layer and an absorbing layer are inserted in the test chambers to enable holding of the allergen material that is to be used in the testing for allergy. When using the testing device according to FIG. 1 of NL-8701577-A, the testing device is applied to the patient's skin by means of a suitable surgical tape while the carrier with its adhesive layer in the embodiments according to FIGS. 2-4 is extended past the long side edges of the flexible strip so as to be directly applied to the skin without necessitating additional tape. In all embodiments, a cover strip is used, which has its own adhesive layer to be able to be temporarily held on the underlying parts of the testing device. A serious drawback of this known testing device is that the allergen material in the test chambers can leak out from the test chambers, on the one hand through the underside of the indentations in the test chamber and, on the other hand, over the actual edge of the frame of the test chamber. When leaking down through the underside of the test chamber, the test allergen reaches the porous tape and can penetrate therethrough and contaminate the patient's clothing. When leaking over the edge of the frame, the test allergen is spread over the skin surface towards neighbouring test chambers. This is a serious drawback since the assessment of the allergy reactions is rendered difficult.